BdERECTA controls vasculature patterning and phloem-xylem organization in Brachypodium distachyon

Kaori Sakai,Angelina D’Orlando,Amy Cartwright,Etienne Delannoy,Sébastien Antelme,Philippe Le Bris,Axelle Bouder,Jean Christophe Palauqui,Debbie Laudencia-Chingcuanco,Richard Sibout,Stéphanie Pateyron,Gregory Mouille,John Vogel,Frédérique Tellier,Sylvie Citerne,Sylviane Daniel

doi:10.1186/s12870-021-02970-2

Abstract

BackgroundThe vascular system of plants consists of two main tissue types, xylem and phloem. These tissues are organized into vascular bundles that are arranged into a complex network running through the plant that is essential for the viability of land plants. Despite their obvious importance, the genes involved in the organization of vascular tissues remain poorly understood in grasses.ResultsWe studied in detail the vascular network in stems from the model grass Brachypodium distachyon (Brachypodium) and identified a large set of genes differentially expressed in vascular bundles versus parenchyma tissues. To decipher the underlying molecular mechanisms of vascularization in grasses, we conducted a forward genetic screen for abnormal vasculature. We identified a mutation that severely affected the organization of vascular tissues. This mutant displayed defects in anastomosis of the vascular network and uncommon amphivasal vascular bundles. The causal mutation is a premature stop codon in ERECTA, a LRR receptor-like serine/threonine-protein kinase. Mutations in this gene are pleiotropic indicating that it serves multiple roles during plant development. This mutant also displayed changes in cell wall composition, gene expression and hormone homeostasis.ConclusionIn summary, ERECTA has a pleiotropic role in Brachypodium. We propose a major role of ERECTA in vasculature anastomosis and vascular tissue organization in Brachypodium.

Highlights

Formation of vasculature was a critical step in plant evolution that allowed plants to colonize the land
The inner organization of the vascular bundles (VB) varies between species and tissues and can be organized in different patterns: collateral, amphicribal or amphivasal
These results suggest that the Leucine-Rich Repeat Receptor Like Kinase (LRR-RLK) BdERECTA is a key factor controlling the anastomosis of vascular tissue in Brachypodium

Summary

Introduction

Formation of vasculature was a critical step in plant evolution that allowed plants to colonize the land. Vascular strands are initiated from primary meristems in which a precise orchestration of hormonal mechanisms control both phyllotaxy and patterning of vascular bundles (VB) [7] Both dicotyledonous and monocotyledonous plants have the same basic primary vascular plan consisting of large acropetally differentiating veins, grass stems are characterized by reiterative phytomers that need to be. When grass vasculature is formed, it lacks the thickening of vascular tissues produced by secondary meristem, the cambium located in an open collateral VB which separate xylem and phloem active in most dicotyledonous plants [8]. We use laser capture microdissection (LCM) to discover genes mainly expressed in nascent VB and to localize BdERECTA in the apical meristem These results suggest that the Leucine-Rich Repeat Receptor Like Kinase (LRR-RLK) BdERECTA is a key factor controlling the anastomosis of vascular tissue in Brachypodium. The genes involved in the organization of vascular tissues remain poorly understood in grasses

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